Studies On SO₄～(2-)-MoO₃-ZrO₂ Solid Superacid Catalyst And Pervaporation Membrane Seperation Esterification

The properties and structures of SO₄^2- — MoO₃—ZrO₂ solid su-peracid catalysts that had not been reported were prepared, and their activities for esterification of acetic acid with n-butanol were measured. The effects of the preparation conditions, such as the MoO₃ content, the calcination temperature, and the concentration of H₂SO₄ on the properties of the catalysts were studied. The lifetime of the catalysts and the mechanism of deactivation were also investigated.The surface acidity and acid strength distribution, the phase structure , the surface composition, and the calcination procedure of the catalysts were analyzed and characterized by Hammett indicator, Py-TPD, XRD, EDX, SEM, DTA/TG, FT-IR and LRS. The results showed that MoO₃ adjusted the acid strength distribution, and increased the content and the thermal stability of SO₄^2- of the catalysts. By incorporation MoO₃ into the catalysts, the crystallization of ZrO₂ was delayed and the metastable tetragonal ZrO₂ (t) was stablized. The stable tetragonal ZrO₂ phase was a necessary structural condition to obtain the superacidity for the SO₄^2-— MoO₃— ZrO₂ catalysts.According to the results of LRS, MoO₃ existed on the catalysts surface in two kinds of surface state, i. e. two-dimensional polymolyb-dates and Mo-O-Zr surface species which formed when the tetra-coordi-...